Why do people take IIMs when they can take FMS Delhi which has such a low fee?

The brand name is the main argument. 

When it comes to items as basic as clothing, people are quite brand aware. Do you believe they wouldn't give a postgraduate degree any thought? And in this case, the brand name serves more than one purpose. It benefits you in a variety of situations. Mostly because of the strong alumni network and connections:

Consider that you wish to launch a business. Most likely, your alumni can and/or will jump to your aid with suggestions and financial support.

Imagine yourself losing your job one day. Your alumni can and/or will come to your aid once more. IIM graduates frequently lend a hand to one another in any manner they can. I believe that a few students from IIM-B couldn't get placed at the end of the year in 2007/2008 (I can't remember exactly). With the help of their networks and contacts, the alumni placed the remainder of the class almost promptly. If I'm not mistaken, IIM-A graduates assisted IIM-B at that time. You can see that they are all extremely helpful.

The most important is at last, the Opportunity for Career Development. An IIM degree can help you flourish in ways that are unparalleled. Of course, a lot depends on how you establish your value within the company. It wouldn't be enough to just have your name or degree. But if two men of equal skill and ability (one an IIM graduate and the other an FMS graduate) were to compete for a job in a corporation, the IIM graduate would unquestionably win.

Additionally, not all IIMs can be considered for this. FMS may unquestionably be placed higher than the newest IIMs.